Girdle assembly for stud mounted rocker arms

ABSTRACT

A girdle assembly for stud mounted rocker arms particularly adapted for use in racing engines wherein it is desired to unify the valve stud structure to prevent stud fatigue failure and adverse harmonics. The valve adjustment mechanism is provided by barrel nuts and locking studs. The barrel nut is externally threaded to accept a lower spherical seating nut on which the girdle rests in counter-bored spherical recesses which mates with the seating nuts. The bar is locked in place and the girdle assembly secured as a unitary structure by bearing washers and lock nuts engaging the upper surface of the bar and urging it into rigid contact with the seating nuts. After assembly and tightening, the girdle assembly need not be loosened or disassembled for valve adjustment, but, the latter can be carried out by adjusting the barrel nuts right through the girdle assembly while the latter is fully tightened.

BACKGROUND OF THE INVENTION

The present invention relates to apparatus for stabilizing the rockerarm assembly of stud mounted rocker arm designs in internal combustionengines operating at high RPM, i.e., from 5000 rpm to 7000 rpm andabove. The invention is applicable to both lifter type and overhead camtype engines that employ stud mounted rocker arms.

Stud mounted rocker arm assemblies have been adapted for many highperformance, high rpm engines, particularly those used in racing.Without stabilization, stud mounted rocker arm are often subject topremature fatigue failure. Even when failure does not result, adverseharmonic vibrations spoil engine performance. Races have been lost tothis problem since these parts cannot be replaced within the timeconstraints of the racing situation. Furthermore, even where studgirdles have been used they have not functioned well at very high rpmsresulting in rough engine performance or difficult adjustment.

Heretofore, girdle bars and plates have been clamped sidewise to severalof the studs at once in order to distribute vibration and to tie therocker arm structure together. Such girdle bar mechanisms are shown inU.S. Pat. No. 3,870,024 to Ridgeway, issued Mar. 22, 1975 and U.S. Pat.No. 3,430,612 to Anseth issued Mar. 4, 1969.

Both of these reference patents propose a mechanical arrangement inwhich a clamp is formed by squeezing a pair of girdle bars partiallyencircling the studs with a small gap between the girdle bars with a setof screws operating intension. This causes the included girdle pairs toclamp the studs laterally, i.e., normal to the axis of the stud. In theso-called Chevy V-8 heads, the studs are aligned parallel and in thesame plane which makes for relatively simple machining of the recessesfor such prior girdles. However, in the Ford V-8 head the valves arecanted and splayed so that there is no common alignment. Economicmachining of a girdle for such an arrangement has not been possible notonly due to the required resetting and rejigging of the machine tools,but also because the installation becomes too critical.

The designs of U.S. Pat. Nos. 3,430,612 and 3,870,024 references rely onscrews in tension for the clamping forces. As known, tensioned screwshave considerable yield and the result is not fully effective as theoperating forces increase. In most cases, moreover, the removal of thegirdle, which must be done several times before each race, requiresseveral very inconvenient and time-consuming steps; requires the use ofboth of the mechanic's hands, one to back the other end of the screwwhile the first is removed. While one handed arrangements appear to beshown in U.S. Pat. No. 3,430,612 they are impractical for other reasons.There is, therefore, a need for a new and improved girdle assembly whichwill overcome the above limitations and disadvantages.

In general, it is an object of the present invention to provide animproved valve stud girdle which is self-aligning to the studs over asuitable range of positions; uses clamping forces developed withoutscrews tension in the plane of the girdle (lateral to the studs), andwhich can readily be removed and replaced after being installed.

A further object of the invention is to provide a valve stud girdle ofthe above character which can be set up, removed and reinstalled in aone-handed operation with high accuracy and in a very short time so asto be suitable for the racing environment.

A further general object is to provide a stud girdle which usesprimarily friction forces in a ball socket joint for transmitting andequalizing vibrations and forces among the rocker valve rocker armstuds.

A further general object to provide a valve stud girdle which canreadily be adapted by a splitting arrangement to divide the same amongstinterspersed rocker arm studs which are canted and splayed, as is FordMotor car engines.

Further general object of this invention is to provide a valve studgirdle assembly for engine heads which results in fewer stud failuresduring operation at high rpms than conventional designs.

A further object of the invention is to provide a valve stud girdlewhich is user-friendly by being easy to install and readily permittingvalve adjustments to be made directly through the girdle while the sameis fully secured in place.

These and other objects and features of the invention will be apparentfrom the following description and claims when taken in conjunction withthe accompanying drawings, of which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a cylinder head, with a girdle assemblyinstalled, constructed in accordance with the present invention for anengine head having canted and splayed rocker arm studs.

FIG. 2 is an elevational view of the cross section taken along lines2--2 of FIG. 1.

FIG. 3 is a cross-sectional view along the lines 3--3 of FIG. 1.

FIG. 4 is an expanded view of the girdle bars of FIG. 1 removed andslightly separated for clarity of illustration.

FIG. 5 is a cross-sectional view taken along lines 5--5 of FIG. 4.

FIG. 6 is a cross-section of the view taken along the lines 6--6 of FIG.4.

FIG. 7 is an isometric view, partially broken away of an alternatecylinder head and girdle assembly constructed in accordance with thepresent invention for engine aligned rocker arm studs lying parallel toeach other in a common plane.

FIG. 8 is a cross sectional view taken along the lines 8--8 of FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1 there is shown a head 10 on an engine of theFord V-8 type with the valve in-head rocker arm assembly 11 and girdlebar assembly 12 installed and constructed in accordance with the presentinvention. As is known, a plurality of push rods 13 extend upwardlythrough passages in the head and are driven by a cam shaft to makecontact with one side 15a-h of a set of rocker arms 16a-h mounted on aset of rocker arm studs 18a . . . 18h. As best shown in FIG. 3 the otherend 20 of the rocker arms carries a roller bearing which is in drivingcontact with the stem ends 27 of the valves through a roller cam 24. Thevalves are set in guides (not shown) and supported for spring loadedreciprocating motion by a conventional double spring 26, 28, valveretainer 30, and keeper 32 arrangement.

The rocker arm 11 and its yoke are free to move up and down the mountingstud 18 under the control of a barrel nut 32 having a lower portion 34internally threaded to engage the length of the rocker arm studs.

The barrel nut 32 is enlarged away from the studs at its upper portion36 which is also internally threaded and supports therein an allen hexstud 38 threaded through the upper end of the barrel and making lockingcontact with the top of the rocker arm stud. The barrel nut 32 isterminated at its head end in an external hex shape 39 to permitadjustment of valve clearance by rotation of the barrel after which thehex stud is screwed with an allen wrench into engagement with the top ofthe stud to place the barrel in locked position under tension. As willbe seen in the following description from an inspection of the drawings,the stud girdle arrangement of the present invention allows this samevalve adjustment procedure to be used without modification even when theentire girdle assembly is in place.

The girdle assembly comprises one or a pair of bars 12a, b together witha hemispherical seating nut 40, bearing washer 42 and locking nut 44.The seating nut is 40 threaded to the barrel nut 32 to support the barfrom the lower side through a mating hemispherical recess. The bar islocked in a position by the locking nut 44 and bearing washer 42 whichthreadedly engages the upper end of barrel nut 32. In the application tothe Ford geometry a pair of bars 12a, 12b is used to accommodate theFord design in which the studs are canted and splayed in two planes.Thus, the load of each bar of the girdle assembly is carried on thethreaded exterior of the set of barrels onto which are screwed the setof spherical seating nuts each having upwardly facing hemispherical ballsections on which the girdle bar rests in a mating hemispherical recess46. More specifically, the ball section is trincated to form a solidfrustrum interseated by two planes, the upper giving relief to that endin contact with the recess and the lower bounded by the hex section.This frustrum of a hemispherical serves as a column in compressionbetween the nut 44 and the bar 12 to secure the same by compression frombeneath and above and in axial alignment with the stud but normal to thebar. Each ball nut has a lower most hex shaped section for wrenchadjustment of elevation.

The structure of the girdle assembly is best shown in FIGS. 4 through 6.The bar 12 is bored on locations spaced for passing the studs and barrelnuts and is counter-bored at 50 from below to form an enlarged sphericalrecess as 46 of the same radius of curvature as the ball nut. The upperside of the bar is also counter-bored at 54 around each hole andsurfaced flat in a plane perpendicular to the axis of the respectivestud. The bores are generally aligned with the position and direction ofthe respective stud and the counter-bore flat is also aligned so that abearing washer and lock nut can seat flat against that surface whenscrewed down over the barrel nut. This brings the girdle into forceableand stabilized position wedged between the upper surface of the ball nutfrom below (seating in the spherical counter-bored recess) and the upperlock nut driving the bearing washer against the upper counter-boredsurface.

Installation of the girdle assembly is straight forward. The barrel nutsare installed with the hex studs free. Each rocker arm to valveclearance is adjusted by turning the barrel nut with a wrench set on thehex head and fixing the adjustment by screwing down the hex stud with anallen wrench.

The set of seating nuts is then installed over the barrel nuts with theouter most pair at each end adjusted up to the desired height of thegirdle, the intervening nuts being lowered out of contact with thegirdle bar. The upper washers and locking nuts are then securly fastenedto the outer most pair of barrel nuts. Then, the remaining seating nutsare screwed up into full seating contact with the recesses in the bar,the remaining upper washers and locking nuts are installed and tightenedto complete the installation.

It is a particular advantage of the present invention that readjustmentof valve clearances can be made with exceptional convenience and withoutany change in the girdle assembly itself. Thus, the selected valve isadjusted by loosening the hex stud and turning the barrel nut rightthrough the locking and seating nuts of the girdle assembly while thelatter remain fully tightened. Of course, the pitch of the stud and thebarrel nut exterior are the same.

As shown particularly in FIG. 4, the Ford head assembly requires thegirdle bar to be divided into mating pairs which have an interiorallyfacing structure which is interleaved so that alternate studs arecarried in alternate ones of the bars 12a, b. In this way the fact thatthere are two different planes in which the valve studs lie can bereadily accommodated without attempting very difficult machiningoperations and while retaining the easy freedom of adjustment. While intheory it may be desirable to have secured all eight (8) of the valvestuds together in a single bar, it is found that the securing of four(4) achieves substantially all of the expected improvement to be gainedin the use of a girdle assembly.

A Chevrolet head 58 is illustrated in FIG. 7 and is characterized byhaving valve studs 60 which lie in a common plane for which reason allof the studs can be readily accommodated in a single girdle bar 62. Across-sectional structure of the bar is shown in FIG. 8 and issubstantially the same as that explained in connection with FIGS. 1-6 sothat like parts have been given like numbers with the addition of aprime ('). As shown, a single, imitary girdle bar can be used for bothsets of studs, which should give better performance with a simpleroverall structure.

What is claimed is:
 1. A girdle assembly for unitary support of a set ofat least three rocker arm studs comprising adjustment means positionedon each stud to adjust valve lash, ball nut means threadedly engagingeach said adjustment means and having a nut portion at its bottom endand a upwardly facing girdle support surface, girdle bar means havingholes therethrough for passing the upper end of said studs andadjustment means, each said holes opening downwardly into a recessthereabout which mates with the support surface of te associated ballnut means, said ball nut means, which when adjusted, define a planarstructure within which said girdle bar means is evenly supported,locking nut means threadedly engaging the upper end of said adjustmentmeans whereby the ball nut means and locking nut means, when taken up,firmly and directly grip the upper and lower surfaces of said girdle barmeans to thereby couple the rocker arm stud set together as a mutuallysupporting assembly.
 2. A girdle assembly for supporting a set of rockerarm studs as a unitary structure for damping vibrations comprising,barrel means positioned on each stud to adjust valve lash, ball nutmeans threadedly engaging each said barrel means and having a nutportion at its bottom and upwardly facing ball surface at its top,girdle bar means having holes therethrough for passing the upper end ofsaid studs and barrel means, each said holes opening downwardly into arecess thereabout which mates with the upper surface of said ball nutmeans, which when adjusted, define a plane within which said girdle barmeans is evenly supported, locking nut means threadedly engaging theupper end of said barrel means whereby the ball nut means and lockingnut means, when taken up, firmly and directly grip the upper and lowersurfaces of said girdle bar means to thereby transform the rocker armstud set and girdle assembly into a mutually supporting assembly.
 3. Agirdle assembly for supporting a set of at least three rocker arm studsas a unitary structure for distribution of vibrations therebetweencomprising, a rocker arm barrel threaded internally and screwed intoplace on each stud to adjust valve lash, said barrel having adjustmentnut portion at its upper end, a locking stud engaging the barrelinterior to its upper end and terminating in an surface adapted to liein contact with the top of said rocker arm stud, a ball nut threadedlyengaging the barrel and having a nut portion on its bottom end and anupwardly facing ball portion on its top forming a surface of a frustrum,a girdle bar means, said girdle bar means having holes therethrough forpassing the upper end of said studs and barrels, each of said holesopening downwardly into a recess thereabout which mates with the surfaceof the frustrum of said respective ball nut, said ball nuts, whenadjusted, defining a plane within which said girdle bar means is evenlysupported, nut and washer means threadedly engaging the upper end ofsaid barrel nut whereby the ball and barrel nut when taken up firmly anddirectly grip the upper and lower surface of said girdle, means forminga flat on the upper side of said girdle and surrounding each said hole,said barrel nut and washer clamping the interposed grid plate from itsupper and lower surfaces in compression resisted by the tension forcesdeveloped in the barrel nut and substantially normal to the plane of thegirdle bar means.
 4. The girdle assembly as in any of claims 1 through 3in which said upwardly facing surface is hemispherical.